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Radiation protection for paediatric patients

Radiation protection for paediatric patients

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Radiation protection for paediatric patients

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  1. IAEA Regional Training Course on Radiation Protection of patients for Radiographers, Accra, Ghana, 11-15 July 2011 Radiation protection for paediatric patients

  2. Why Talk about radiation protection during radiological procedures in Children The number of imaging tests using ionizing radiation are increasing around the world !!! And…. • Children are of special concern in radiation protection: • Higher radiation sensitivity • Longer life expectancy • Identical settings provide higher organ doses than in adults • More susceptible to radiation damage Radiation Protection in Paediatric Radiology L01. Why talk about radiation protection in paediatric radiology

  3. Generators For paediatric examinations, the generator should be: a high frequency multi-pulse (converter) of sufficient power nearly rectangular waveform with minimal voltage ripple Radiation Protection of Children in Screen Film Radiography Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  4. Exposure time When children are uncooperative they may need immobilization They have faster heart and respiratory rates Short exposure times improve quality without increasing dose Only possible with powerful generators and accurate exposure time switches Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  5. Additional filtration Additional filtration may lead to dose reduction 0.1 mm of Cu in addition to 2.5 mm of Al* reduce ESAK by 20% barely noticeable reduction in image quality Some modern systems canautomatically insert either 0.1mm or 0.2 mm Cu depending on the examination Equipment, practice, dose and image quality *Cook, V., Imaging, (13) 2001:229–238 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  6. Exposure factors Increased kVp (reduced mAs): Greater penetration and less absorption Reduced patient dose for a constant film density Neonatal chest: Minimum 60kVp: less contrast but better assessment of lung parenchyma Lower kVp if looking for bone detail Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  7. Antiscatter grid Often unnecessary in children because smaller irradiated volume (and mass) results in less scattered radiation. Limited improvement in image quality but increased dose of ~50% with the use of antiscatter grids Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  8. Equipment, practice, dose and image quality Automatic Exposure Control (AEC) • Generally not appropriate for small children • Sensors (size and geometry) are normally designed for adult patients • AEC use may be associated with the use of the grid (where the grid is not removable), which is frequently unnecessary • AEC should have specific technical requirements for paediatrics • If not appropriate oravailable, carefully applied exposure charts are preferred Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  9. Equipment, practice, dose and image quality Focus-to-film distance (FFD) • Longer focus-to-film distances • Smaller skin dose • Combined with a small object-to-film distance, results in less magnification (less geometric distortion) and improved quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  10. Equipment, practice, dose and image quality Image receptors • Fast screen-film combinations have advantages (reduction of dose) and limitations (reduced resolution) • Low-absorbing materials in cassettes, tables, etc., are specially important in paediatric radiology (carbon fibre) Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  11. Collimation • Require a basic knowledge of paediatric pathology • Lung fields extremely large in congestive heart failure & emphysematous pulmonary diseases • Diaphragm, high in intestinal meteorism, chronic obstruction or digestive diseases • Beam-limiting devices automatically adjusting the field size to the full size of the cassette are inappropriate for children • Minimal deviation from the radiation and light beam may have large effects in relation to the usually small field of interest - check light beam diaphragm regularly Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  12. Equipment, practice, dose and image quality Shielding • Standard equipment of lead-rubber shielding of the body in the immediate proximity of the diagnostic field • Special shielding has to be added for certain examinations to protect against external scattered and extra-focal radiation Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  13. Shielding The eyes should be shielded for X-ray examinations involving high absorbed doses in the eyes, e.g., for conventional tomography of the petrous bone, when patient cooperation permits The absorbed dose in the eyes can be reduced by 50% - 70% In any radiography of the skull the use of PA-projection rather than the AP-projection can reduce the absorbed dose in the eyes by 95% 13 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  14. Patient Positioning and Immobilization Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  15. Immobilization devices must be easy to use Their usefulness should be explained to the accompanying parent(s) Radiological staff members should only hold a patient under exceptional circumstances Even in quite young children the time allocation for an examination must include the time to explain the procedure not only to the parents but also to the child Patient Positioning and Immobilization Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  16. Mobile radiography • Mobile radiography is valuable on occasions when it is impossible for the patient to come to the radiology department • It can result in • poorer quality images • unnecessary staff and patient exposures • Where practicable, X-ray examinations should be carried out with fixed units in an imaging department • Mobile units should only be used with those who cannot safely be moved to such a unit Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  17. Radiation Protection of Children in Digital Radiography Accurate collimation Dose parameter monitoring Avoid use of grid Increase FSD Shielding sensitive organs Use manual settings Reprocess-rather than repeat non diagnostic images

  18. Radiation Protection of Children in Fluoroscopy and Interventional Radiology Optimization Positioning, collimation, selection of optimised exposure factors are essential in fluoroscopy. Use “Child Size” protocol and lowest dose protocol possible for patient size, frame rate, and length of run A removable grid should be available, and normally only used with children > 8 years. Acknowledge fluoroscopy timing alerts during procedure

  19. Equipment, Practice, Dose and Image Quality Focus-to-Skin Distance • The patient should be positioned as close as possible to the image intensifier • The X-ray tube should be as far away as possible from the patient’s table in order to avoid excessive skin dose Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  20. The image intensifier/detector should be placed as close to the patientas possible • (< 5 cm) for better image quality and reduced dose (undercoach systems) Bad practice Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  21. Anti-scatter Grid Anti-scatter grid should be removable in pediatric equipment, particularly fluoroscopic systems No grid is recommended for small children resulting in a dose reduction up to 50% Magnification Magnificationshould be avoided unless necessary Using a field of view of less than 12 cm may result in four times the dose of a 25 cm diameter field. Digital radiography allows post-processing magnification with no increase in dose Equipment, Practice, Dose and Image Quality Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  22. Changing from a large field of view to an increased magnification increases the exposure required by the image intensifier tube The absorbed dose to tissues within the beam is also increased Example: Field of view, diameter 25 cm Dose rate= 0.3 mGy/s Field of view, diameter 17 cm Dose rate = 0.6 mGy/s Field or view, diameter 12 cm Dose rate = 1.23 mGy/s. Magnification Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  23. Exposure factors Low tube potential (50–60 kV) fluoroscopy provides better demonstration of low to moderate contrast examinations, e.g. those with iodinated contrast medium (200–300 mmol) or dilute barium (100 mg %) In combination with heavy tube filtration (0.25 mm copper), can improve quality and reduce dose Tube current and beam on time are directly proportional to dose Equipment, Practice, Dose and Image Quality Tapiovaara MJ et.al., Phys Med Biol. 1999 44(2):537-59 Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  24. Filtration Additional tube filtration may allow dose reductions 0.1mm Cu should be incorporated into all modern systems used in a paediatric setting Dose reduction by 20% without affecting image quality Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  25. Automatic Brightness Control Specific kV/mA dose rate curves for automatic brightness control (ABC) should be used in fluoroscopic systems for children An ABC giving a pre-set controlled tube potential (kV) and variable tube current (mA) and allowing ‘‘dose hold’’ is preferred Equipment, Practice, Dose and Image Quality Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  26. Equipment, Practice, Dose and Image Quality Pulsed Fluoroscopy All new equipment should have pulsed fluoroscopy Variable pulse rates are possible Grid controlled pulsed fluoroscopy X-ray tubes: allows very short exposures with very little soft radiation The lowest pulse rate will usually produce the lowest dose, depending on whether there is a compensatory increase in tube current (mA) to maintain quality Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy 26

  27. Equipment, Practice, Dose and Image Quality Shielding Use lead gonad protection whenever possible Repeating an examination due to overuse of shielding is poor practice Lead apron, into beam path – reduce light output from the II – System will automatically increase amount of X-rays to achieve same light output as before!! => Increase patient dose - BEWARE Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy 27

  28. Mobile Fluoroscopy • Mobile C-Arms should have the option of removing the anti-scatter grid • Particular attention should be given to collimation, fluoroscopic time and displayed KAP measurements • Trained staff should operate C-arms especially in pressure environments such as theatres Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

  29. Radiation Protection of Children During Computed Tomography One size does not fit all...

  30. Equipment, Protocol, Dose and Image Quality • Spiral or helical scanning is preferable in paediatrics as an entire volume is image • Short tube rotation times reduce movement artefacts and provide more detailed cardiac imaging • Immobilization devices vs sedation • PA scout image Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  31. Equipment, Protocol, Dose and Image Quality Image thickness: • Should be chosen depending on the size of the child and the application • Use maximal acquisition collimation (assuming this would result in scanning at lower mA) appropriate for specific diagnosis • Narrow collimation in MSCT and 1 mm slices on some SDCT result in a higher dose (increase in mAs to maintain image quality) Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  32. Equipment, Protocol, Dose and Image Quality Pitch: • SDCT: a pitch factor 1.5 is recommended for most examinations • 25% reduction in dose compared with using a pitch of 1 • MDCT: reduction in dose due to greater pitch may not beachieved • tube current (mA) can beautomatically adjusted to keep the dose and noise the same Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  33. Equipment, Protocol, Dose and Image Quality Tube potential (kVp) • There are few advantages to using a high tube potential (kV). • Without a reduction in tube current (mA) this leads to a significantly higher dose. • 100 kVp or 80 kVp is usually adequate for children. • Lowering of kVp enhances contrast • Be aware that images with high noise, even if they do not look very crisp, may provide the diagnostic information. Lower tube current (mA): Should be used. High tube current is required only when there is a need for high image detail ( in low contrast settings) Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  34. Equipment, Protocol, Dose and Image Quality Gantry Tilt • A straight gantry results in irradiation of a smaller volume of tissue compared with a tilted gantry and is recommended. • Exception: tilt is used to avoid unnecessary exposure of sensitive tissues, e.g. in brain CT for avoiding the orbits. Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  35. Equipment, Protocol, Dose and Image Quality Scan Length • Scan the minimum length required and be restrictive in defining upper and lower limits. • Optimise scan parameters for volume coverage by using representative volume sample(s) when the entire volume is not needed (by sequential scans with gaps) to reduce dose-length product Vock and Wolf , Dose Optimization and Reconstruction in CT of children, in Radiation Dose from Adult and Paediatric MDCT, Springer, 2007 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  36. Shielding The bismuth eye shield is simple to place and covers only the eye In-plane shields are associated with greater image noise and streak artifacts. However, shields reduce radiation dose. Automatic exposure control did not increase radiation dose when using a shield. Karla et al, Korean J Radiol. 10:156-63, 2009 This adult patient has a 3 layer bismuth latex eye shield in place. While artefact is seen into the globe, no artefact is transmitted into the brain. Standoff pads can reduce surface artefact Hopper KD, et al, Am J Neuroradiol 22:1194–1198,2001 Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

  37. Example of successful story I Arch and Frush, AJR 2008;191:611–617: Since 2001, kVp and mA settings, two principal parameters determining radiation dose, have decreased significantly for paediatric body MDCT It is a reasonable assumption that these changes are due to efforts to increase awareness about the risks of radiation Paediatric chest CT Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 37

  38. Example of successful story II Wallace, et al. Proceedings of IRPA 12, Buenos Aires, 2008, FP0227: Eight paediatric hospitals Training and seminars on optimisation Dose reduction greater than 50% Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 38

  39. http://www.pedrad.org/associations/5364/ig/ Radiation Protection in Paediatric Radiology L07. Radiation protection in interventional radiology 39

  40. THANK YOU! Radiation Protection in Paediatric Radiology L01. Why talk about radiation protection during radiological procedures in children